Gas separator

ABSTRACT

A gas separator for use in a downhole production system includes a duct structure and a pump intake shroud.

PRIORITY AND INCORPORATION BY REFERENCE

This application claims the benefit of U.S. Provisional PatentApplication No. 62/222,025 filed Sep. 22, 2015 entitled GAS SEPARATOR.

This application incorporates by reference, in their entireties and forall purposes U.S. Pat. Nos.: 8,545,190 filed Apr. 23, 2010; 8,955,601filed Apr. 19, 2011; 9,027,654 filed Oct. 23, 2013; and, 9,356,484 filedMay 1, 2014.

This application incorporates by reference, in their entireties and forall purposes U.S. Pat. App. Pub. Nos.: 2012-0199210 filed Apr. 13, 2012;2013-0146798 filed Jan. 21, 2013; 2015-0184487 filed Feb. 27, 2015;2015-0233207 filed May 1, 2015; and, 2009-0065202 filed Sep. 10, 2007.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a system and method for removing gasfrom a fluid flow. In particular, a duct structure supplies a fluid to apump intake shroud.

Discussion of the Related Art

Where a fluid will be pumped, separating gas from the fluid beforehandmay be beneficial. Known fluid/gas separators can perform this task in avariety of environments.

Among the most demanding environments for fluid/gas separators is thesubmersed pump environment as in a well for producing a gas laden fluidsuch as a hydrocarbon fluid. Challenges here include severe spaceconstraints and required high reliability while performing under varyingand often unpredictable operating conditions.

Having developed several acceptable downhole oil/gas separator designs,new oil/gas separator solutions appear to be of little interest to theindustry. Rather, with proven solutions in hand the industry typicallyavoids the risks of developing new technologies as reputational andfinancial costs of failed oilfield experiments likely exceed theperceived value of the new technology.

An exemplary downhole oil/gas separator solution is found in U.S. Pat.Pub. No. 2009/0065202 filed Sep. 10, 2007. Here, a well fluid pumpingapparatus comprises a rotary pump, a gas separator mounted to the pump,a shroud surrounding the gas separator, and a passage extending from agas separator outlet through the shroud for discharging lightercomponents to a shroud exterior.

SUMMARY OF THE INVENTION

The present invention incorporates a duct structure that supplies afluid to a pump intake shroud.

In an embodiment, A gas separator for use in a downhole productionsystem, the gas separator comprises: a biduct for installation in acased downhole production string including a pump; the pump forinstallation between production tubing and the biduct; the biduct forinstallation between the pump and reservoir tubing; a pump inlet shroudforming an annular sump for the pump; a supply duct of the biduct forreceiving flow from the reservoir tube and for discharging reservoirflow to an annulus bounded by the casing; and, a recirculation duct ofthe biduct for receiving flow from the annulus bounded by the casing;wherein the pump sump is charged when (i) flow from the supply ductpools over the sump and (ii) flow from the recirculation duct emptiesinto the sump.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanyingfigures. These figures, incorporated herein and forming part of thespecification, illustrate the invention and, together with thedescription, further serve to explain its principles enabling a personskilled in the relevant art to make and use the invention.

FIG. 1 shows a schematic diagram of the gas separator of the presentinvention incorporated in a portion of a fluid production string.

FIG. 2 shows an embodiment of the gas separator of FIG. 1.

FIG. 3 shows an embodiment of the gas separator of FIG. 1

FIG. 4 shows a flow diagram of the gas separator of FIG. 3.

FIGS. 5A-B show duct structures with rectangular cross-sections for usewith the gas separator of FIG. 3.

FIGS. 5C-D show duct structures with triangular cross-sections for usewith the gas separator of FIG. 3.

FIG. 6 shows a duct structure with a triangular cross-section for usewith the gas separator of FIG. 3.

FIG. 7 shows an embodiment of the gas separator of FIG. 1 utilizing abiduct with a common dividing wall.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The disclosure provided in the following pages describes examples ofsome embodiments of the invention. The designs, figures, and descriptionare non-limiting examples of certain embodiments of the invention. Forexample, other embodiments of the disclosed device may or may notinclude the features described herein. Moreover, disclosed advantagesand benefits may apply to only certain embodiments of the invention andshould not be used to limit the disclosed invention.

To the extent parts, components and functions of the described inventionexchange fluids, the associated interconnections and couplings may bedirect or indirect unless explicitly described as being limited to oneor the other. Notably, indirectly connected parts, components andfunctions may have interposed devices and/or functions known to personsof ordinary skill in the art.

FIG. 1 shows a schematic of the present invention incorporated in aportion of a fluid production string 100. A pump 110 with a pump intake108 and a pump intake shroud 111 takes suction from a fluid sump 107.The fluid sump is filled via a duct structure 106 that receives fluidfrom a fluid supply 102 such as a hydrocarbon well. Fluid leaves thepump via a pump discharge 112. In some embodiments, a valve such as abypass valve 114 with a spill port 116 is fluidly coupled between thepump discharge and a production tubing string 118. In variousembodiments, the inlets, outlets and ports are one or more of a fitting,flange, pipe, or similar fluid conveyance. The bypass valve 114 may beany suitable bypass valve such as one of the valves of U.S. Pat. Nos.8,545,190, 8,955,601, 9,027,654 or one of the valves of U.S. Pat. Pub.Nos. 2012-0199210, 2013-0146798, 2015-0184487, 2015-0233207.

FIG. 2 shows a gas separator of the present invention installed in adownhole location 200. A casing 222 encircles production tubing 220 thatis fluidly coupled with a pump 210 and more particularly with a pumpoutlet 211. A gas separator including a duct structure 206 fluidlycouples a pump intake 213 with a reservoir tube 230.

The pump is for receiving fluid from a fluid supply such as ahydrocarbon reservoir 102. As shown, the pump receives fluid 232 fromthe reservoir tube 230 via the gas separator 206 and moves the fluid 224through the production tubing 220 for recovery, for example at a surfacelocated well head.

In various embodiments, an annular passageway(s) 215 is formed betweenthe casing 220 and one or more of the production tubing 220, pump 210,gas separator 206, and reservoir tubing 230. Gas that is separated fromthe fluid received 232 from the reservoir 102 may be discharged 226 asgas bubbles 250 from the gas separator 206 into a fluid pool 260 in theannular passageway 215. An annular packer or sealing ring 228 seals theannulus 215 below the gas discharge 226 to enable recovery of theseparated gas, for example at a surface located well head.

FIGS. 3-4 show a gas separator of the present invention. In FIG. 3 thegas separator is shown installed in a downhole location 300. The gasseparator is installed in a production string including a pump andproduction tubing arranged substantially about a longitudinal x-x axis.In FIG. 4 schematic flow paths are shown 400.

Similar to FIG. 2, a casing 322 encircles production tubing 320 that isfluidly coupled with a pump such as an electric submersible pump havingan upper pump section 341 and a lower motor section 343. A gas separatorincludes a pump inlet shroud 340 and a duct structure 348 that fluidlycouples the pump and a reservoir tube 353.

The pump is for receiving fluid from a fluid supply such as ahydrocarbon reservoir 102. As shown, the pump receives fluid 354 fromthe reservoir tube 353 and moves the fluid 332 through the productiontubing 320 for recovery, for example at a surface located well head.

In various embodiments, an annular passageway(s) 335 is formed betweenthe casing 322 and one or more of (i) the production tubing 320, (ii)pump inlet shroud 340, duct structure 348, and (iii) reservoir tubing353. An annular packer or sealing ring 352 seals the annulus 335 nearthe duct structure 348 to enable recovery of the separated gas 333, forexample at a surface located well head.

As seen, the pump inlet shroud 340 is a figure of revolution, forexample a can, about the pump 341. A lower end of the shroud 343interconnects with the duct structure 348 and an upper end of the shroud339 is spaced apart from the production tubing 320 such that a shroudannulus 337 and an annular shroud inlet 338 are formed. In variousembodiments, the shroud annulus provides a sump for the pump 341.

During normal operation, a fluid level 336 in the annulus 335 pools overthe pump and motor 341, 343 such that pump operation transfers fluidfrom the annulus to the production tubing 320. Fluid from the annulus335 reaches the pump 341 by (i) entering 375 through the pump shroudannulus 338 from the casing annulus 335 and (ii) passing through 350,344 the duct structure 348.

FIG. 4 shows an embodiment of selected fluid paths of the gas separatorof FIG. 3 where the duct structure 348 includes a supply duct 368 and arecirculation duct 378.

The supply duct 368 receives fluid 354 from the reservoir tubing 353.Fluid leaving 346 the supply duct pools over the pump 341 and motor 343as it fills the casing annulus 335 and the shroud annulus 338 to a fluidlevel 336 above the shroud upper end 339. Pump operation moves fluid 342from the shroud annulus to the production tubing 332. Gas bubbles 334that reach the pooled fluid surface 336 collapse to produce a gas flow333 in the casing annulus.

The recirculation duct 378 receives fluid 350 from the pooled fluid inthe casing annulus 335. Fluid leaving the recirculation duct 344 entersthe shroud 340 near the motor 343. Pump operation moves the fluid 344from the shroud annulus 337 to the production tubing 332. In variousembodiments, the fluid flow 344 is directed to cool the motor 343. Insome embodiments, the fluid flow 344 impinges on the motor.

Gas that is separated from the fluid supplied 354 from the reservoirtube 353 is discharged 346 from the duct structure 348 into the casingannulus 335.

FIGS. 5A-D show schematic diagrams of embodiments of alternative ductstructures 500A-D.

FIG. 5A shows a duct structure or duct structure portion 500A includingsupply 510 and recirculation 520 ducts having a somewhat rectangularcross-section. Fluid 512 from a fluid reservoir 102 enters the supplyduct 510 in a direction about parallel to the longitudinal x-x axis andexhausts 514 into the casing annulus 335 in a direction aboutperpendicular to the longitudinal x-x axis.

Fluid 522 from the casing annulus 335 enters the recirculation duct 520in a direction about perpendicular to the longitudinal x-x axis andexhausts 524 into the shroud annulus 337 in a direction about parallelto the longitudinal x-x axis.

FIG. 5B shows a duct structure or duct structure portion 500B includingsupply 530 and recirculation 540 ducts having a somewhat rectangularcross-section. Notably, the ducts share a common central or dividingwall 535. Fluid 532 from a fluid reservoir 102 enters the supply duct530 in a direction about parallel to the longitudinal x-x axis andexhausts 534 into the casing annulus 335 in a direction aboutperpendicular to the longitudinal x-x axis.

Fluid 542 from the casing annulus 335 enters the recirculation duct 540in a direction about perpendicular to the longitudinal x-x axis andexhausts 544 into the shroud annulus 337 in a direction about parallelto the longitudinal x-x axis.

The duct structure of FIG. 5B may be referred to as a “biduct” with acommon dividing wall while the duct structure of FIG. 5A may be referredto as a biduct without a common dividing wall.

FIG. 5C shows a duct structure or duct structure portion 500C includingsupply 550 and recirculation 560 ducts having a somewhat triangularcross-section. Fluid 552 from a fluid reservoir 102 enters the supplyduct 550 in a direction about parallel to the longitudinal x-x axis andexhausts 554 into the casing annulus 335 in a direction aboutperpendicular to the longitudinal x-x axis.

Fluid 562 from the casing annulus 335 enters the recirculation duct 560in a direction about perpendicular to the longitudinal x-x axis andexhausts 564 into the shroud annulus 337 in a direction about parallelto the longitudinal x-x axis.

FIG. 5D shows a duct structure or duct structure portion 500D includingsupply 570 and recirculation 580 ducts having a somewhat triangularcross-section. Notably, the ducts share a common central or dividingwall 575. Fluid 572 from a fluid reservoir 102 enters the supply duct570 in a direction about parallel to the longitudinal x-x axis andexhausts 574 into the casing annulus 335 in a direction aboutperpendicular to the longitudinal x-x axis.

Fluid 582 from the casing annulus 335 enters the recirculation duct 580in a direction about perpendicular to the longitudinal x-x axis andexhausts 584 into the shroud annulus 337 in a direction about parallelto the longitudinal x-x axis.

The duct structure of FIG. 5D may be referred to as a biduct with acommon dividing wall while the duct structure of FIG. 5C may be referredto as a biduct without a common dividing wall.

FIG. 6 shows a duct structure 600 including supply 610 and recirculation620 ducts having a somewhat triangular or wedge shaped cross-section.Notably, the ducts share a common central or dividing wall 615. Fluid612 from a fluid reservoir 102 enters the supply duct 610 in a directionabout parallel to the longitudinal x-x axis and exhausts 614 into thecasing annulus 335 in a direction about perpendicular to thelongitudinal x-x axis.

Fluid 622 from the casing annulus 335 enters the recirculation duct 620in a direction about perpendicular to the longitudinal x-x axis andexhausts 624 into the shroud annulus 337 in a direction about parallelto the longitudinal x-x axis.

In an embodiment, the duct structure 600 is substantially coaxiallyarranged about the longitudinal x-x axis and includes a substantiallycircular inlet mouth 630 of diameter dl and an opposed substantiallycircular outlet mouth 632 of diameter d2. The inlet mouth receives aninlet flow 612 and the outlet mouth exhausts an outlet flow 624.

By virtue of the dividing wall 615 of the duct structure 600, the ductstructure is divided to provide a supply lumen 631 that is isolated froma recirculation lumen 633. In the supply lumen, the direction of flow640 is toward a sidewall outlet 613 and in the recirculation lumen thedirection of flow 642 is from a sidewall inlet 623.

In the supply lumen 631 the flow cross-sectional area decreases from theinlet mouth 630 toward the sidewall outlet 614 such that the flowvelocity is increased along this path. And, in the recirculation lumen633 the flow cross-sectional area increases from the sidewall inlet 623toward the outlet mouth 632 such that the flow velocity is decreasedalong this path.

Various embodiments provide a sidewall outlet 614 via perforations inthe sidewall (as shown). And, various embodiments provide a sidewallinlet 623 via perforations in the sidewall (as shown). Other embodimentsmay utilize one or more nozzles integral with the sidewall or notintegral with the sidewall rather than perforations.

The sidewall outlet 614 may be designed to provide a pressure dropacross the outlet that tends to release gas that is in solution with thefluid 640. The recirculation lumen 633 may be designed to provide apressure rise through the lumen that tends to dissolve gas in the fluid642.

FIG. 7 shows a gas separator of the present invention installed in adownhole location 700. The gas separator is installed in a productionstring including a pump and production tubing arranged substantiallyabout a longitudinal x-x axis.

A casing 722 encircles production tubing 720 that is fluidly coupledwith a pump such as an electric submersible pump having an upper pumpsection 741, a pump seal 765, and a lower motor section 743. A gasseparator includes a pump inlet shroud 740 and a duct structure 748 thatfluidly couples a pump inlet 763 and a reservoir tube 753. The ductstructure 748 is similar to the duct structure of FIG. 6.

The pump 741 is for receiving fluid from a fluid supply such as ahydrocarbon reservoir 102. As shown, the pump receives fluid 754 fromthe reservoir tube 753 and moves the fluid 732 through the productiontubing 720 for recovery, for example at a surface located well head.

In various embodiments, an annular passageway(s) 735 is formed betweenthe casing 722 and one or more of (i) the production tubing 720, (ii)pump inlet shroud 740, (iii) duct structure 748, and (iv) reservoirtubing 753. An annular packer or sealing ring 752 seals the annulus 735below the duct structure 748 to enable recovery of the separated gas733, for example at a surface located well head.

As seen, the pump inlet shroud 740 is a figure of revolution, forexample, a can, about the pump 741. A lower end of the shroud 773interconnects with the duct structure 748 and an upper end of the shroud739 is spaced apart from the production tubing 720 such that a shroudannulus 737 and an annular shroud inlet 738 are formed. In variousembodiments, the shroud annulus provides a sump for the pump 741.

During normal operation, a fluid level 736 in the annulus 735 pools overthe pump 741, seal 765, and motor 743 such that pump operation transfersfluid from the annulus to the production tubing 720. Gas recoverable 733from the casing annulus 735 may result from gas that comes out ofsolution to form gas bubbles 734 that collapse near the pool surface736.

The shroud annulus 737 is charged with fluid when fluid from thereservoir tube 753 passes 754, 746 through a supply duct 782 of the ductstructure 748 into the casing annulus 735 and then passes 775 from thecasing annulus into the shroud annulus 737 to feed 742 the pump inlet763.

The shroud annulus 737 is charged with fluid when fluid from the casingannulus 735 passes 750, 744 through a recirculation duct 784 of the ductstructure 748 into the shroud annulus 737 to feed 745 the pump inlet763.

The present invention has been disclosed in the form of exemplaryembodiments. However, it should not be limited to these embodiments.Rather, the present invention should be limited only by the claims whichfollow where the terms of the claims are given the meaning a person ofordinary skill in the art would find them to have.

What is claimed is:
 1. A gas separator assembly for use in a gasproduction system, the assembly comprising: a biduct for installation ina cased downhole production string that includes a pump taking suctionfrom a hydrocarbon reservoir; the pump for installation betweenproduction tubing and the biduct; the biduct for installation betweenthe pump and reservoir tubing, the biduct having a longitudinal axis; apump inlet shroud forming an annular pump sump; a biduct supply duct forreceiving flow from the reservoir tubing and for discharging reservoirflow to an annulus bounded by the casing; and, a biduct recirculationduct for receiving flow from the annulus bounded by the casing; whereinthe pump sump is charged when (i) flow from the supply duct enters thepump shroud and (ii) flow from the recirculation duct enters the sump.2. The gas separator assembly of claim 1 further comprising: a commondividing wall that is shared by the supply duct and the recirculationduct.
 3. The gas separator assembly of claim 2 further comprising: arectangular cross-section of the supply duct; a rectangularcross-section of the recirculation duct; wherein the flow received bythe supply duct is received in a direction parallel to the longitudinalaxis and discharged in a direction perpendicular to the longitudinalaxis; and, wherein the flow received by the recirculation duct isreceived in a direction about perpendicular to the longitudinal axis anddischarged in a direction about parallel to the longitudinal axis. 4.The gas separator assembly of claim 2 further comprising: a triangularcross-section of the supply duct; a triangular cross-section of therecirculation duct; wherein the flow received by the supply duct isreceived in a direction parallel to the longitudinal axis and dischargedin a direction perpendicular to the longitudinal axis; and, wherein theflow received by the recirculation duct is received in a direction aboutperpendicular to the longitudinal axis and discharged in a directionabout parallel to the longitudinal axis.
 5. A gas separator assembly foruse in a gas production system, the assembly comprising: a biduct forinstallation in a cased downhole production string that includes a pumpfor producing a fluid flow from a hydrocarbon reservoir; the pump forinstallation between production tubing and the biduct; the biduct forinstallation between the pump and reservoir tubing, the biduct coaxiallyarranged about a longitudinal axis; a biduct central dividing wallisolating a wedge shaped supply lumen from a wedge shaped recirculationlumen; the biduct including a circular inlet mouth and an opposedcircular outlet mouth; in the supply lumen, a flow path cross-sectionalarea decreases from the inlet mouth toward a sidewall outlet; and, inthe recirculation lumen, a flow path cross-sectional area increases froma sidewall inlet toward the outlet mouth.
 6. The gas separator assemblyof claim 5 wherein the sidewall outlet is provided via a perforatedportion of a supply lumen sidewall.
 7. The gas separator assembly ofclaim 5 wherein the sidewall inlet is provided via a perforated portionof a recirculation lumen sidewall.
 8. A gas separator assembly for usein a downhole production string, the gas separator assembly comprising:a biduct and a shroud for encircling a pump, the biduct including asupply duct and a recirculation duct; within a well casing, the pump forproducing liquid from a hydrocarbon reservoir; the pump for locationbetween production tubing and the biduct; the biduct for locationbetween a base of the pump shroud and reservoir tubing; the casing andthe pump shroud forming an outer annulus therebetween; the pump shroudand the pump forming an inner annulus therebetween; wherein duringoperation the annuli are flooded with liquid such that the pump takessuction from a sump within the pump shroud, the inner annulus and sumpbeing supplied with liquid i) that earlier entered the outer annulus viathe supply duct and ii) from the recirculation duct; and, wherein duringoperation the supply duct provides a pressure drop sufficient to releasegas that is in solution with the liquid passing therethrough.
 9. A gasseparation method for separating gas from a liquid and for producing theseparated gas via a downhole production string, the method comprisingthe steps of: providing a biduct supply duct for flooding an outerannulus between a casing and a pump shroud with hydrocarbon liquid;supplying a pump sump within the pump shroud with liquid from the outerannulus that overflows the pump shroud; providing a biduct recirculationduct for recirculating liquid from the outer annulus to the pump sump;in the supply duct, providing a liquid pressure drop sufficient torelease gas dissolved in liquid moving therethrough; and, in therecirculation duct, providing a liquid pressure rise sufficient todissolve gas in the liquid moving therethrough; wherein an annulusbetween the casing and production tubing collects the separated gas. 10.The gas separation method of claim 9 further comprising the steps of:providing a biduct wall common to the supply duct and the recirculationduct; coaxially arranging the biduct and the pump shroud; in the supplyduct, providing a converging flow path to provide a liquid pressure droptherethrough; and, in the recirculation duct, providing a diverging flowpath to provide a liquid pressure rise therethrough; wherein the biductis bounded by upper and lower planes, the lower plane including a supplyduct inlet that is coupled to reservoir tubing and the upper planeincluding a recirculation duct outlet that empties into the pump sump.11. The gas separation method of claim 10 wherein the biduct is in theform of a cylinder enclosing an internal dividing wall that is sloped,the internal dividing wall separating the supply and recirculation ductssuch that the supply duct has an inlet diameter that is about the sameas a cylinder inside diameter and the recirculation duct has an outletdiameter is about the same as the cylinder inside diameter.